With continuous development of mobile communications in the future, three-dimensional beamforming technology has drawn more and more attentions. Massive MIMO is considered as one of key technologies for the next generation mobile communication (5G). FIG. 1 shows an example of a scenario of a multi-user multiple input multiple output (MU-MIMO) system with massive antennas, in which one base station and multiple user equipment are arranged in a cell and the base station is provided with massive antennas to provide services to the multiple user equipment. Since massive antennas are provided in the base station, a spatial resolution of the system is improved. In a case where an array of the antennas is a planar array, three-dimensional beamforming may be implemented. Some research has been made on the three-dimensional beamforming technology under a condition of massive antennas in the conventional technology. In the conventional technology, the three-dimensional beamforming is usually implemented by providing the same number of radio frequency chains as the antennas. However, in a case where massive antennas are deployed, cost of radio frequency may become very high, and technical complexity of the system may be also high. In order to reduce the cost and the complexity, the hybrid three-dimensional beamforming technology using a smaller number of radio frequency chains in the system with massive antennas has drawn more and more attentions, but little research has been performed in this aspect at present.